Rapid increases in air pollution are associated with more than double the odds of myocardial infarction (MI), which is similar to the impact of sustained exposure to poor air quality, a study has found.1
“Our study suggests that the risk of heart attack associated with nitrogen oxides depends on the dynamics and extent of increases, and not only on exposure to high concentrations,” said the senior author, Florian Rakers, from Jena University Hospital in central Germany.
He warned, “The impact of rapid increases in air pollutants on heart health may be at least as important as absolute concentrations.” He added that these rapid rises can occur in smaller cities generally regarded as having low levels of air pollution, noting, “Increases of nitric oxides of more than 20 micrograms/m3 within 24 hours happen more than 30 times per year in Jena, which is known as a ‘clean air’ city where statutory limits for nitric oxides are generally not violated.”
The researchers retrospectively studied all 693 patients admitted to Jena University Hospital with an MI from 2003 to 2010. They looked at levels of air pollution in the city in the three days before each patient’s symptoms began and compared them with pollution levels in the previous and subsequent week. Each patient served as his or her own control.
The results, reported in the European Journal of Preventive Cardiology,1 showed that rapid, large increases in nitrogen oxide levels (>20 micrograms/m3 within 24 hours) were associated with more than double the odds of MI (odds ratio 2.21 (95% confidence interval 1.19 to 4.08)).
In a similar way, rapid increases of nitrogen dioxide of more than 8 micrograms/m3 were associated with 73% higher odds of MI (1.73 (0.91 to 3.28)). The odds of MI decreased by 60% after a drop in NO2 concentration of greater than 8 micrograms/m3 (0.40 (0.21 to 0.77)), suggesting a close to linear association.
Results of ozone concentrations were ambiguous, while rapid change in the levels of particulate matter (PM10) were not associated with MI risk.
“Our results suggest that the risk of MI associated with nitrogen oxides is dependent not only on long or short term exposure to a high ambient concentration of these gaseous pollutants but also on the dynamic and extent of their increase,” said the authors.
They warned, “Rapid increases of nitrogen oxides are not uncommon even in apparently clean air cities but are not reflected in current EU statutory limits.” They called for larger studies to confirm their findings and develop policy recommendations.
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